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I have configured my PC to turn it on by WOL and WOW (By DDNS). Both of them are working correctly, the problem is that if the PC remains off for a few hours, the WOW no longer works, but the WOL continues to work. But if I turn on the PC and turn it off, the WOW works again. Does anyone have any idea what might be going on? Thank you so much!

Roman Racca
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  • Are you using Windows on your computer? Last time i played around with WoL it was a hassle, due to network adapter settings needed to be tweaked in Windows before computer booted up - even though it should be only a BIOS issue. – Lasse Michael Mølgaard May 24 '20 at 12:47
  • Yes, it is Windows. Both Windows and BIOS settings are OK, since WOL always works and WOW only works for a while. That is the strange thing. – Roman Racca May 24 '20 at 14:09

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Okay here is my list of places where I look in order to get Wake-On-LAN working.

First off: WoL must be enabled in BIOS (ofc).

In windows: Check the settings for the network adapter and make sure "wake on magic packet" is enabled.

When you shut down your computer it also matter if it is shutting down in S3 (sleep mode), S4 (hibernate) or S5 (soft power off mode).

According to Microsoft WoL only works with S3 or S4. It does not work with fast startup or soft shut off (S5).

Now in theory a WoL packet has to be sent to the subnet broadcast address (like 192.168.1.255) and have the following content:

FF FF FF FF FF FF
(Target MAC Address repeated 16 times)

Spaces added for readability.

... but it has been my experience, that you sometimes have to use the host ip address instead - and still use MAC address inside the data packet.

And last setting try is to sent the packet to destination UDP port 7 or alternatively UDP port 9.

My experience is that it varies which combination works.

So to recap all these conditions has to be double checked:

  • WoL enabled in BIOS
  • Magic packet enabled on network adapter in Windows.
  • Does the computer shutdown to S3 or S4?
  • Do you have to send to broadcast address or host ip address?
  • Check if machine responds on UDP port 7 or 9.

All in all quite few places to stumble in order to get WoL to work.

Lasse Michael Mølgaard
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